1. Field of the Invention
The present invention generally relates to devices for coupling interchangeable tools to universal handles and, more particularly, is concerned with an interchangeable tool coupling assembly having a spring-biased locking sleeve.
2. Description of the Prior Art
In the electrical utility industry, considerable work is done by use of elongated insulated tools or "hot sticks." To minimize the number of such sticks required to be carried by line crew members, universal handles and interchangeable tools have been developed.
There are two basic types of coupling means used between the universal handles and interchangeable tools. A first basic type is a disc-shaped coupler having protruding teeth mateable with similar teeth on the interchangeable tools. A bolt or screw in the center of the disc-shaped coupler holds a tool and handle together while the teeth hold the parts in alignment.
A second basic type is a hex-shaped coupler having a ferrule member on the end of the handle which has a hex shape with a female threaded center hole, much like a hex nut. The interchangeable tools have a male threaded member with a hex shape which matches the hex shape of the ferrule member. To install the tool, a line crew member screws the male threaded member into the female threaded center hole of the hex shaped ferrule member until it is nearly tight, making sure the flats of the two hex shaped members are in alignment. A collar, which has an internal female hex shape, is then slid down over the male hex shaped member and female hex shaped ferrule member to a locking position, preventing the tool from unscrewing from the handle.
To retain the collar in the locking position, for many years a spring-loaded ball has been provided in the collar which becomes engaged in a groove provided on the male member when the collar reaches the locking position. However, this proved unsatisfactory as the collar could be unlocked by a cross arm or the like accidentally hitting the collar. One approach to preventing the accidental unlocking was to install a cotter pin in a through hole behind the collar after it was in the locking position. This approach worked positively, but required a supply of cotter pins as they became bent and unusable. Another approach, one still in use today, is a molded plastic "C" clip with a protruding pin. The clip is slipped over the tool behind the collar and the protruding pin inserts into the same through hole as was used by the cotter pin. This is an improvement in that the clip is reusable many times over and does not require replacement because of deformation.
In practice, however, the clips are difficult to use by line crew members wearing their standard gloves and therefore either become lost or not used. In addition, the protruding pin being made of plastic can be sheared off by a force imposed on the collar from hitting a cross arm or the like.
Consequently, a need remains for an approach which will provide an effective and comprehensive solution for the aforementioned problems associated with the prior art devices used for the coupling of universal handles and interchangeable tools and without introducing any new problems in place thereof.